Consolidated Statements of Comprehensive Income/(Loss) (Parenthetical) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Successor [Member]
Income tax (expense)/benefit on unrealized gains (losses) related to available-for-sale securities	$ (0.1)		$ (0.3)
Income tax (expense)/benefit on unrealized gains (losses) related to derivative activity	(0.3)		3.4
Income tax (expense)/benefit on reclassification of earnings related to derivative activity	0		0.7
Income tax (expense)/benefit on reclassification of earnings related to pension and postretirement activity	0		0
Predecessor [Member]
Income tax (expense)/benefit on unrealized gains (losses) related to available-for-sale securities		0.2		0.2
Income tax (expense)/benefit on unrealized gains (losses) related to derivative activity		25.9		30.2
Income tax (expense)/benefit on reclassification of earnings related to derivative activity		(1.0)		(1.3)
Income tax (expense)/benefit on reclassification of earnings related to pension and postretirement activity		0.1		0.7
THE DAYTON POWER AND LIGHT COMPANY [Member]
Income tax (expense)/benefit on unrealized gains (losses) related to available-for-sale securities	(0.1)	0.1	(0.3)	(1.3)
Income tax (expense)/benefit on unrealized gains (losses) related to derivative activity	1.3	0	2.2	0.8
Income tax (expense)/benefit on reclassification of earnings related to derivative activity	0.1	0.9	0.7	0.3
Income tax (expense)/benefit on reclassification of earnings related to pension and postretirement activity	$ (0.6)	$ (0.1)	$ (1.7)	$ 0.7